The present invention relates to a drive for a foodstuff-packaging machine. More particularly this invention concerns such a drive for a bottling machine.
In a standard packaging or bottling machine such as described in U.S. Pat. No. 4,862,933 of B. Gies an endless conveyor is provided with a longitudinal succession of holders each forming a respective transverse row of seats for respective containers, normally bottles. The conveyor has at least one straight and horizontal stretch which passes a series of subassemblies that serve sequentially to sterilize, fill, and cap the containers. Typically the conveyor moves discontinuously, that is in steps, picking up empty bottles at an upstream end of the straight stretch, sterilizing, filling, and closing the bottles, and depositing them on an output conveyor at a downstream end of the stretch.
The standard such conveyor comprises a pair of standard roller chains spanned over sprockets at least one of which is driven at a predetermined rate by a respective drive motor. The normally discontinuous advance is carefully set with respect to the cycling time of the sterilizing, filling, and capping units so that each time the chain stops, the containers are positioned under the nozzle, sealing tool, or the like of the respective unit.
With time it is inevitable, even with an essentially inextensible metal roller chain, for there to be some offset between the desired position of a row of bottles at the starting of a sterilizing, filling, or capping cycle and its actual position. The result can be failure to properly sterilize, partial filling and spillage, and inadequate sealing of the container closure. The sealing machine must normally bring a heated or ultrasonic tool into engagement all around the mouth of the container to seal perfectly, and the fillers often have a nozzle that must fit into the mouth of the bottle. Obviously any failure of these devices requires that the batch be thrown out and the machine reset. Since the drive motor that advances the holder chain is invariably offset from the sterilizing, filling, and closing machines, wear resulting in stretch or lengthening of the chain can be enough to set holders in bad position.
It is therefore an object of the present invention to provide an improved drive for a container-filling machine.
Another object is the provision of such an improved drive for a container-filling machine which overcomes the above-given disadvantages, that is which ensures perfect synchronism between the sterilizing, filling, and/or closing units and the normally discontinuous advance of the conveyor.
An apparatus for filling containers has according to the invention a frame carrying a plurality of sprockets and an endless conveyor chain on the frame having between two of the sprockets a straight treatment stretch. A succession of holders secured to the chain are each formed with a transverse row of seats adapted to hold respective containers. Respective machines carried on the frame and spaced apart along the stretch clean, fill, and cap containers in the seats. A drive connected to one of the sprockets advances the chain and moves the containers in steps in the seats past the machines. A metering wheel journaled in the frame meshes near one of the machines with the chain such that as the chain is advanced the wheel is synchronously rotated. A movable sensor element synchronously movable with the wheel can orbit on rotation of the wheel past a fixed sensor element carried on the frame to generate an output. A controller connected between the movable sensor element and the drive receives the output and positions the seats with respect to the machines.
Thus the system of this invention determines the actual position of the holders carried by the chain right at the machine that is sterilizing, filling, or closing the containers in the holders. If the chain stretches or wears, the position is still measured right where it counts, even with the drive motor connected to the chain at a location relatively remote from the various treatment machines.
According to the invention a metering shaft journaled in the frame has one end carrying the metering wheel and another end carrying a disk on which is mounted the movable sensor element. The angular position of the movable sensor element is adjustable on the disk. In addition the movable sensor element is mounted on an outer periphery of the disk. It can be set on the disk at such an angular position that the sensor elements come into closest proximity with each other at a time when the holders are immediately upstream of a desired stopping position so that inertia of the chain is compensated for by the angular offset of the movable sensor element. The sensors are of the noncontacting type and may work magnetically, with light, or even capacitatively.
The wheel according to the invention has teeth meshing with the conveyor chain. Furthermore an effective circumference of the wheel at the teeth is equal to a longitudinal spacing between succeeding holders on the conveyor chain. Thus one revolution of the wheel exactly equals one step of the chain.
In accordance with the invention the conveyor chain has a pair of opposite edges and the described metering wheel meshes with one of the edges. The apparatus further has according to the invention a second metering wheel journaled in the frame and meshing across the conveyor from the first-mentioned metering wheel with the other edge of the chain such that as the chain is advanced the second wheel is also synchronously rotated. A second movable sensor element synchronously rotatable with the second wheel orbits on rotation of the second wheel past a second fixed element to generate an output. The controller is connected to both of the fixed sensors and measures how much time elapses between generation of the outputs by the fixed sensor elements. More particularly the controller stops the chain when the outputs of the fixed sensors are not generated within a predetermined time of each other. Thus if the conveyor chain becomes racked, that is with one edge advanced more than another, the system will be shut down, as this is indication of a serious problem.